Man, this freaked me out for a few seconds until it reset itself. I press play on a project then press the play button again to pause the playback. I then press the play button again and the STOP button is not usable for several seconds after the play button is pressed. I would like to add that if the mouse is not hovering over the transport that the stop button resets quicker. I have done a 12 second count at one point before the STOP button is usable.
 
1. Open project
2. Put NOW time at the middle of the project.
3. Press play
4. Press play again to pause
5. Press play and leave mouse hovering over play button
6. Repeat 4-5 a couple times and it extends the recovery time for the STOP button to reset for use
 
There are varying times when the STOP button will get reset for use with the mouse.

I haven't tried it, but I suspect it's related to this:
http://forum.cakewalk.com/sonar-X3d-now-time-playhead-Lag-when-moving-the-mouse-cursor-on-playback-m2952126-p2.aspx
 

The mouse is not moving at all. I will call support to verify when they open shop.
 
this is 100% repro-able here

could it be related to this http://forum.cakewalk.com/FindPost/2966308

man, I bounced SONAR and now the issue is gone. At least it is documented if someone else runs into it and the search function works in the forum...

Sounds like a driver state issue. Never seen anything like that, but I rarely use the transport module to start/stop/pause - I use Spacebar and Ctrl+Spacebar.

yea - next time it happens, see if the spacebar will stop - that's what I always use

Yup I cannot repro almost certainly drivers or hardware/firmware (forget #2). Thanks.

I have had this occur on two projects, I would click play and the stop button is unavailable for varying amounts of time up to 20 seconds. After a complete reboot of windows the issue would disappear. I just assumed it was a driver that stopped working properly and the reboot obviously corrected it.
Don't remember where my head was at the time but I didn't even think of using the spacebar to stop playback. Doh!
I haven't seen the issue again since those two times.